SAO PAULO, April 30 (Reuters) - Brazilian food retailer GPA said on Tuesday it joined a Sao Paulo state tax renegotiation program, allowing it to slash a 3.6 billion reais ($693 million) tax debt by about 80%.

Under the program, the company would pay a tax debt liability of 794 million reais to Sao Paulo state in 120 monthly installments adjusted by Brazil's benchmark Selic interest rate.

GPA noted that the impact on its cash flow will be "substantially mitigated" by the termination of another tax settlement in July, adding that the expected net impact is an expense of about 261 million reais. ($1 = 5.1936 reais) (Reporting by Paula Arend Laier; Writing by Andre Romani; Editing by Chris Reese and David Alire Garcia)